One important step in determining a price for your product is to determine how much it's actually worth. But what does that mean?
Your product is worth exactly the same amount as the cost of not using your product. Analyze the way prospective customers currently achieve the goals your product would satisfy and determine the costs they face in achieving these goals.
No, "negative pricing" does not mean paying your customers to use your product. It's the term I use for basing the price of your product on how much it costs for your customers not to use it.